CVE-2021-3424: Keycloak IDN Homograph Attack
Summary
CVE-2021-3424: Keycloak is vulnerable to IDN homograph attack. Affects org.keycloak:keycloak-services versions < 18.0.0. Fixed in 18.0.0. How to fix ↓
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Background
Keycloak is an open-source identity and access management solution that provides single sign-on capabilities. It is commonly used in enterprise environments to secure applications and services. The vulnerability identified as CVE-2021-3424 affects the keycloak-services package in the Maven ecosystem. This vulnerability allows for IDN homograph attacks, where a malicious user can register with a name that is visually similar to an already registered user, tricking the admin into granting additional privileges.
Vulnerability Detail
The vulnerability arises from a flaw in the Keycloak implementation. By exploiting IDN homograph attacks, an attacker can deceive the admin into believing they are granting privileges to an existing user, while in reality, they are granting them to the attacker. This can lead to unauthorized access, privilege escalation, and potential compromise of sensitive data. The vulnerability has a CVSS score of 5.3, indicating a moderate severity level.
How To Fix
Latest published version: 26.8.1 as of 23 Oct 2026
Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
18.0.0
This is the first release that contains the fix.
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Workaround
There is no known workaround for this vulnerability. It is essential to apply the recommended fix by upgrading the keycloak-services package to a secure version.
Conclusion
The IDN homograph attack vulnerability in Keycloak can have serious consequences, including unauthorized access and data compromise. It is crucial to apply the recommended fix by upgrading the keycloak-services package to a secure version. For further support on vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for org.keycloak:keycloak-services →
FAQ
Keycloak is an open-source identity and access management solution that provides single sign-on capabilities.
An IDN homograph attack is a type of attack where a malicious user registers with a name that visually resembles an already registered user, tricking the admin into granting additional privileges.
This vulnerability can lead to unauthorized access, privilege escalation, and potential compromise of sensitive data.
The vulnerability has a CVSS score of 5.3, indicating a moderate severity level.
To fix this vulnerability, it is recommended to upgrade the keycloak-services package to version 18.0.0 or later.
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